Apparatus for making grids



Oct. 2, 1 945.

W. W. EITEL I APPARATUS FOR MAKING GRIDS Original Filed Aug. 24, .1942 2Sheets-Sheet 1 d/JCK BY Y sLmq M EU R m o m w w W r6 ME mm W M T W Oct.2, 1945. w w rr 2,385,973

APPARATUS FOR MAKING GRIDS Original Filed Aug. 24, 1942 2 Sheets-Sheet 2INVENTORS WILL/AM M EITEL JACK ALMS CUL OUGH 114M 5%,

THEIR ATTORNEY Original a plication, 2.4,: it

456,126,,nowPatentNo.2,35,9 514,datcd Qctohen r T 1 1 3,129.44. Dividedand thisapplicatiorrMarch 29,,

943, Serial No'. 431.045

This is, a, division. of our copending application, Serial No. 456,126,filed August 24, 1942, in which is claimed the method embodying theimprovements of our invention, while this application is particularlydirected to the apparatus.

Our invention relates to the manufacture of a cage-type grid electrodefor electronic tubes.

It is among the objects of our invention to provide an improved mandrelupon which the grid is formed, whereby the grid bars are more accuratelypositioned and uniformly tensioned.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing, will be set forth in the followingdescription of our invention. It is to be understood that we do notlimit ourselves to this disclosure of species of our invention, as wemay adopt variant embodiments thereof within the scope of the claim.

Referring to the drawings:

Figure l is a side elevational view of our improved mandrel having agrid formed thereon; and

Figure 2 is an end view of the same.

Figures 3 and 4 are fragmentary sectional views of the mandrel atdifferent stages of forming the grid; and

Figure 5 i a diagrammatic side elevational view illustrating our method.

In terms of broad inclusion, our grid-making mandrel comprises anelongated core having. wire receiving slots in the top end thereof, andwire engaging pegs on the core arranged in an annular row spaced fromthe slotted end. Wire receiving grooves are also preferably provided inthe core, extending between the pegs and the slotted end. The grid isformed by securing an end of a wire to the mandrel, looping the wire upalong a side and over the top and down along the opposite side of themandrel to form a pair of grid bars, hooking the wire over a perelooping the wire over,

the end of the mandrel to form another pair of grid bars, hooking thewire over another peg, and continuing the looping and hooking stepsuntil the desired number of grid bars are made.

In greater detail, and referring to the drawings, the grid is formed ona mandrel comprising an elongated cylindrical core 2, preferably ofcopper, having a lower extension 3 providing a handle. This core has adiameter substantially equal to the inside diameter of the grid. Theupper end of the core has a recess 4 bounded by an annular flange 6having a series of radial wire receiving slots 1. Twenty-four slots areshown, it being the row of pegs completes the mandrel structure.

pending onthenumber, of, grid. bars. 8. desired. 3

An annular row of radial pegs 9 is spaced below the upper end of thecore a distance depending upon the length of grid desired. In a mandrelfor a 24-bar grid there are twelve of these pegs. The base ends of thepegs are spaced from the surface of core 2 bya collar H press-fittedonto the core and on which the pegs are integrally formed. A flange I2is also preferably formed on the collar ahead of pegs 9 and has a seriesof twenty-four wire spacing slots l3 aligned with the edges of the pegs.Wire receiving grooves l4, preferably cut at a slight angle to themandrel axis, are provided in core 2 between pegs 9 and slots 1. A tiepin I5 on handle 3 adjacently below Our method of making the gridcomprises fastening an end of a wire I6 to a fixed element 11, and tyingthe other end to mandrel pin IS. The operator then turns the mandrelcounterclockwise as viewed in Figure 3 about an axis transverse to themandrel axis to loop the wire up along a side and over the top and downalong the opposite side of the core to form a pair of the grid bars 8.These bars thus lie along grooves l4 and are connected at the top by abight l8' engaging a pair of the slots I. The operator then hooks thewire about peg 9; again turns the man- 'drel about the transverse axisto reloop the wire over the end; and hooks the wire about another peg,thus forming another pair of grid bars. These looping and hooking stepsare continued until all twenty-four grid bars are laid. The other end ofthe wire is then tied to pin l5 and released from fixed element l1. Atthis stage the grid structure appears as shown in Figure 3.

Recess 4 at the end of the mandrel core provides space for bights l8criss-crossing at the top. In fabricating a grid having a large numberof bars, bights I8 are preferably laid offcenter through slots 1 so thatthe crossovers come at different points instead of all piling up at thecenter. See Figure 2.

Since the bases of pegs 9 are spaced from the surface of core 2, gridbars 8 diverge outwardly toward the pegged ends, and thus lie in conicalformation. The slope of the bars is illustrated in Figure 3. This is toapply tension to the wire bars when ring 2| is applied.

Ring 2| is a metallic band having a diameter slightly larger than core 2so that it fits snugly over bars 8 lying in shallow grooves I 4. Thering is engaged over the top end of the mandrel and is forced inwardlyover the bars to the final position shown in Figure 1; the structurewith ring 2| applied also being illustrated in Figure 4. As the wiresare constricted inwardly from initial conical formation toward thecylindrical surface of; eqre z 2': they are put under tension. 5

This strai'ghtens out the bars and brings them into parallelism, witheach bar lying in its re spective groove I4.

Inasmuch as the grid at this stage is all one 2,385,973 r v T functionsas an electrode) and another electrode .22 engaged'wlth the outersurface of ring 2! as illustrated in Figure 4. Subsequently, one or morewire helixes 2 3 are welded to bars}, and a wire piece of Wire, merelylooped back and forth on the mandrel, there is a compensating action ormovement permitted between the'several lengths of wire when ring 2| isforced on; This tends to equalize the tension in bars 8, and preventsthe wires from breaking; it being further noted that 15 there are nowelds betweerithe wires or between the wires and ring H to break loosewhen tension is being applied.

Ring 2| forms the terminal element at the base of the final gridstructure, and is therefore 20 weldedit'obars 8;-f"lhis'is done bypassing a suitablewelding current through the mandrel (which ring 24 isweldedto the bars adjacent the top of the grid. Core 2 is also used asan electrode for this welding. The wires are then severed at the loweredge of ring 2 I, and the completed grid is slipped off the end of themandrel.

* We claim: e

A mandrel for making a cage-type wire grid, comprising a core alongwhich the wire may be laid toform longitudinal bars of the grid, wirereceiving slots at one end of said core spacing the barscircumferentially about the core, and

' wire engaging pegs arranged in an annular row remote from said end forholding the bars away from the surface of the core, whereby the barsdiverge outwardly from said end toward the pegs.

WILLIAM W. EITEL. JACK A. McCULLOUGI-I.

